Antibiotics III Flashcards
Ciprofloxacin (2nd gen.), Levofloxacin, Gatifloxacin and Moxifloxacin all inhibit DNA synthesis and are members of the class of antibiotics known as _____.
Fluoroquinolones
What do fluoroquinolones target in G- and G+ organisms, respectively?
G- = Gyrase
G+ = Topoisomerase IV
What added constituent of the fluoroquinolones increases their antimicrobial activity
Fluorine
Which fluoroquinolone is most effective against G- organisms?
Ciprofloxacin
others equal in efficiency, but less than cipro
T/F Cipro is the most effective quinolone against G+
FALSE
Cipro is the least effective quinolone against G+ organisms. Others are equal in efficiency, and more effective than cipro.
From least to most, order the quinolones in regard to their actiity against anaerobes.
Cipro
What kinds of infections are quinolones used to treat (6)?
1) UTI
2) Prostitis
3) GI/Abdominal (Traveler’s diarrhea, Shigellosis, Typhoid)
4) Respiratory (Atypical pneumonias [mycoplasma], S. pneumoniae)
5) Bone/joint/soft tissue (Chronic osteomyelitis, polymicrobial diabetic ulcers)
6) STDs (chlamydia, chancroid)
Which STDs are never treated with fluoroquinolones due to resistance?
Syphilis and gonorrhea
Which organisms are beginning to gain resistance to fluoroquinolones (3)?
1) S. aureus
2) P. aeruginosa
3) S. marcescens
Which fluoroquinolone is used to treat anthrax and tularemia?
Ciprofloxacin
Combinations of fluoroquinolones are used to treat _____ or for _____
Atypical mycobacteria or neutropenic prophylaxis
T/F Fluoroquinolone is administered via IV
FALSE
Administered orally (can send patients home with it!)
Metronidazole and Nitrofurantoin is under the class of antibiotics known as _____
Nitroimidazoles
What is metronidazole’s mechanism of action?
Converted to radical iron by ferredoxin, causing fragmentation of DNA
Metronidazole is used to treat _____ and _____.
Strict anaerobes (c. diff)
Parasites (trichomonas, giardia, entamoeba)
T/F Metronidazole can’t be used against organisms that use oxygen, including facultative anaerobes
TRUE
These organisms have the biological components to deal with free radicals
Nitrofurantoin is used almost exclusively to treat _____ or _____
Cystitis or lower UTIs
Nitrofurantoin is effective against many _____ bacteria except _____, AND _____
Effective against many GRAM - bacteria except PROTEUS AND PSEUDOMONAS
The sulfonamides function as _____ antagonists
Folate antagonists
Sulfonamides are competitive inhibitors of _____
Dihydropterate synthase
The enzyme sulfonamides competitively inhibits (dihydropterate synthase) is needed for the production of _____. Blocking this enzyme prevents the organism from _____.
Dihydropterate synthase is needed for the production of THF
Blocking this enzyme prevents the conversion of uracil to thymidine by the organism
What are the mechanisms of bacterial resistance to sulfonamides?
1) New folic acid pathway
2) Altered affinity of enzyme for drug
3) Efflux
Sulfonamides are concentrated in _____, making them _____ in this location
Concentrated in urine (great for UTIs!)
Bactericidal there
Which sulfonamide is used for opthalmologic infections?
Sulfacetamide
Which sulfonamide is used to prevent infection and treat infection of burn wounds?
Silver Sulfadiazine
What are the therapeutic uses of Sulfonamides (4)?
1) UTI
2) Nocardiosis
3) PJP (sulfamethoxazole + trimethoprim [bactrim])
4) Toxoplasmosis
Rifamycins are _____ spectrum
Broad spectrum
Which rifamycin is used for HIV+ patients?
Rifabutin
What are the therapeutic uses of rifampin (3)?
1) TB
2) Staph
3) Meningococcus prophylaxis
What are the therapeutic uses of ridabutin/rifapentine (2)?
1) TB in HIV+
2) MAC
T/F Rifaximin is readily absorbed in the gut.
FALSE
Rifamixin is limited to the lumen of the gut
What is the mechanism of action of rifamycins?
Inhibit DNA-dependent RNA polymerase
How is bacterial resistance to rifamycins achieved?
Alteration of target (DNA-dependent RNA polymerase)
What is the mechanism of action of daptomycin?
Depolarizes bacterial membrane > K+ efflux > death
What kind of organisms does daptomycin cover?
Aerobic G+ cocci (except Pneumonias - drug inactivated by lung surfactant)
- Works against MRSA, MSSA, VRE
What is the mechanism of action of Polymyxins?
Membrane detergent
What kind of organisms do the polymyxins cover? What are the exceptions?
G- organisms EXCEPT Proteus, Serratia, Burkholderia
Which polymyxin is nephrotoxic?
Polymyxin E
What are the first line anti-mycobacterium antibiotics?
Rifampin
Isoniazid
Pyrazinamide
Ethambutol
RIPE Therapy
(Streptomycin)
What are the second line anti-mycobacterium abx?
Cycloserine Amikacin Moxi/Gatifloxacin Ethionamide Aminosalicylic Aid Linezolid
CAME to Alleviate Lung
Isonazid (INH) prevents the synthesis of _____
Mycolic acids
Is isoniazid bactericidal or bacteriostatic?
Trick question. It’s both.
Bactericidal for growing cells
Bacteriostatic for resting cells
Isoniazid (INH) is a prodrug that requires _____ for activation
Catalase peroxidase
Ethambutl inhibits _____ involved in cell wall synthesis of mycobacterium
Arabinosyl transferase
Pyrazinamide is bactericidal at _____ pH, as in a macrophage or phagolysozome
Acid pH
What gene is inactivated by pyrazinamide?
Fatty acid synthase I gene
Which antimycobacterium drug targets the C subunit of mycobacterium ATP synthase?
Bedaquiline (Resistance is acquired by mutating the C subunit)
